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[jacopo <question670169@xxxxxxxxxxxxxxxxxxxxx>]

New question #670169 on Yade:
https://answers.launchpad.net/yade/+question/670169

hi i'm new in YADE. I have a question about packing simulations. I m doing a particles deposition in a script and in another one i m doing a crash impact of a falling mass. The parameters of the falling mass are fixed. I have to work on a soil modeling. I m doing a lot of test and i notice that sometimes if i repeat two times the same deposition, and i export it in the script impact, i obtain different value of "force-impact". The results aren't so different but are different. I m near to the value that i have to reach, but now that i m not changing so much the deposition parameters value  ( like poisson = 0.2 and then poisson=0.21 and same for young).
the problem is: (if i obtained a force impact of 420 kN with a young 16671305 and i change it in  15690640, that is lower, i obtain a higher value(470), and if i repeat the deposition with the same young i obtain again another value, near the first one but not the same. the %error is not so big but however we are talking about kN, but i m expected that repeating the test with the same value it will return the same result.
 
is something wrong on my code??
so is it possible that yade give me a range of values??
 and if yes how can i avoid it and be more precision? 

( the second script is always fixed, i only change the name of the "particles deposited positions" and upload the choosen material parameters) 

script:
from yade import pack, plot
from yade import export, ymport
from yade import export, ymport


O.bodies.append(geom.facetCylinder(center=(0,0,1.25), radius=5.35, height=2.5, orientation=Quaternion((0, 0, 1), 0), segmentsNumber=100, wallMask=6, angleRange=None, closeGap=False, radiusTopInner=-1, radiusBottomInner=-1))

pred=pack.inCylinder(centerBottom=(0,0,0),centerTop=(0,0,2.15),radius=5.34)

idSoil=FrictMat(density=1460,frictionAngle=radians(28),label='soil',young=15690640,poisson=0.2)

O.materials.append(idSoil)	

spheres=pack.randomDensePack(pred,radius=0.08,color=(0,0,1),spheresInCell=2000,memoDbg=False,memoizeDb=None,material='soil')

O.bodies.append(spheres)


O.engines=[
   ForceResetter(),
   InsertionSortCollider([Bo1_Sphere_Aabb(),Bo1_Facet_Aabb()]),
   InteractionLoop(
      
      [Ig2_Sphere_Sphere_ScGeom(),Ig2_Facet_Sphere_ScGeom()],
      [Ip2_FrictMat_FrictMat_FrictPhys()],
      [Law2_ScGeom_FrictPhys_CundallStrack()]
   ),
   NewtonIntegrator(gravity=(0,0,-9.81),damping=0),
   PyRunner(command='checkUnbalanced()',iterPeriod=10),
]

O.trackEnergy=True

############################################################################
######################### DEFINING FUNCTIONS ###############################
############################################################################


def checkUnbalanced():
   if O.time > 2.5 :
      O.pause()
      export.textExt('depoDENSITA1460Y160P20F28.txt',format='x_y_z_r',comment='Final state of the spheres')


O.dt=.8*PWaveTimeStep()
O.run()
#O.stopAtIter=maxIt;
O.saveTmp()


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